L = 1;
s = 0.4;

Point(1) = {-L/2., -L/2., 0, s};

line[] = Extrude{L,0,0}{ Point{1}; };
surface[] = Extrude{0,L,0}{ Line{line[1]}; };
volume[] = Extrude{0,0,L}{ Surface{surface[1]}; };

Physical Volume(1) = {volume[1]};

Transfinite Surface "*";
Recombine Surface "*";
Transfinite Volume "*";